Stop for power and free conveyors

ABSTRACT

A power and free conveyor has trolleys driven along a fixed track by abutments on the trolleys being engaged by dogs depending from an endless drive chain. At a station, a stop is spring-biassed into an operative position in which it depresses the abutment of a trolley out of the path of the dogs. A bellcrank lever has one arm which can be moved into that path. When a dog turns the one arm, the other arm retracts the stop, and the dog then moves the trolley from the station. Thereupon, the trolley releases a latch which holds the stop retracted, so that the stop returns to its operative position.

United States Patent Wilkinson Mar. 14, 197 2 [54] STOP FOR POWER AND FREE 3,347,171 10/1967 Torrance ..lO4/l72 S VEY RS CON 0 FOREIGN PATENTS OR APPLICATIONS 1 K [72] Henfmdshm Er'gland 245,593 4/1969 U.S.S.R. ..104/172 5 [73] Assignee: Geo. W. King Limited, Stevenage, Hertfordshire, England Primary Examiner-Arthur L. La Point Assistant ExaminerRobert Saifer [22] Fned' May 1970 Attarney-Waters, Roditi, Schwartz & Nissen [2]] Appl. No.: 34,972

[57] ABSTRACT [30] Foreign Application Priority Data A power and free conveyor has trolleys driven along a fixed track by abutments on the trolleys being engaged by dogs de- June 6, 1969 Great Britain ..28,892/69 pending from an endless drive chain. At a Station a Stop is spring-biassed into an operative position in which it depresses (g1. ..l04/250, 104/172 the abutment of a trolley out of the path of the dogs A crank lever has one arm which can be moved into that path. [58] Field of Search ..104/249, 250, 252, 172 S when a dog turns the one arm, the other arm retracts the stop and the dog then moves the trolley from the station. Thereu- [56] References Cited pon, the trolley releases a latch which holds the stop retracted, UNlTED STATES PATENTS so that the stop returns to its operative position.

3,437,054 4/1969 Bishop ..104/178 5 Claims, 4 Drawing Figures Patented March 14, 1972 I5 Sheets-Sheet 1 Patented March 14, 1972 5 Sheets-Sheet 2 Patented March 14, 1972 3 Sheets-Sheet 5 STOP FOR POWER AND FREE CONVEYORS This invention relates to conveyors of the kind wherein load-carrying trolleys are propelled along a fixed track by virtue of the engagement with drive abutments on such trolleys of drive dogs which depend from an endless driven chain caused to travel along a path vertically above the aforesaid fixed track. The drive abutments carried by the trolleys are so arranged that while they normally assume a projected or upstanding position wherein they will be contacted by the depending dogs on the driven chain, they are nevertheless capable of depression or downward displacement into a position wherein they will be out of the path of said drive dogs, the arrangement being such that when a drive abutment on a trolley is so depressed the drive dogs on the driven chain will merely travel idly over the top of the trolley and no drive will be imparted to the latter.

It is a main object of the present invention to evolve a stop mechanism which may be installed at any selected point along the path of a conveyor of the kind indicated to effect automatic stoppage of any load trolley at such point without in any way interrupting the travel of the driven chain, there also being provision for releasing the trolley and continuing the drive thereto when required.

According to the invention in a conveyor of the kind indicated it is proposed to provide a stop mechanism adapted to be installed at a selected station along the conveyor path, such mechanism comprising a stop member adapted normally to assume an operative position wherein it will be effective to depress the drive abutment on any load-carrying trolley arriving at the station thereby to effect discontinuance of the drive to such trolley and a member which, when it is required to release the trolley from the station, is moveable into the path of the drive dogs on the driven chain, such member being adapted, when contacted by one of said drive dogs, to be moved to cause retraction of the stop member from its operative position thereby to allow the drive abutment on the trolley to return to its operative position so that the trolley may then be driven from the station there also being means operative as the trolley is driven away from said station to ensure return of the stop member to its initial operative position in readiness for a further operational sequence.

In order that the invention may be clearly understood and readily carried into effect reference will now be made to the accompanying drawings in which:

FIG. 1 is a perspective view illustrating a small part of a conveyor of the kind with which the invention is concerned,

FIG. 2 is a side elevational view of a stop mechanism,

FIG. 3 is a sectional view on the line A-A of FIG. 2, and

FIG. 4 is a plan view of the mechanism shown in FIG. 2.

Referring initially to FIG. 1, which illustrates diagrammatically a small section of a conveyor of the kind with which the invention is concerned, denotes a load-carrying trolley which is equipped with a depending load bar 11 from which loads to be conveyed are suspended. Load-carrying trolleys such as that indicated at 10 are propelled along a fixed track 12 hereinafter termed the trolley track, by means of an endless driven chain 13 which is supported at spaced points along its length by means of so-called chain trolleys one of which is indicated at 14. The chain trolleys run on a second fixed track 16, hereinafter termed the chain trolley track, disposed vertically above the track 12. The chain 13 is provided at spaced points along its length with depending pusher dogs 17 which are adapted to cooperate with driving abutments on the loadcarrying trolleys and to cause the latter to be propelled along the track 12. In the embodiment illustrated, l8 denotes the driving abutment on the trolley 10.

. In known manner each trolley is equipped with an upstanding retainer abutment 19 which will be effective to prevent uncontrolled forward movement of the trolley relative to the chain 13. To allow for indexing of load trolleys i.e., for stoppage of a trolley at one or more selected points along the conveyor path without any interruption of the drive to the chain 13 the drive abutment 18 on each trolley is so mounted as to be capable of retraction into a position wherein it will lie out of the path of the pusher dogs 17 on the chain. The retainer abutment 19 on each trolley I0 is so mounted that while being free to pivot forwardly, i.e., in the direction of travel of the trolley, it will be held against movement past the vertical position in a rearward direction. As indicated above, conveyors of the kind described with reference to FIG. 1 are generally well known and further description thereof is not considered necessary.

Referring now to FIGS. 2-4, 12 again denotes the track along which load-carrying trolleys are caused to travel while 16 again denotes the chain trolley track which serves to support the chain trolleys from which the endless driven chain is suspended. The stop mechanism of the: invention is as will be seen clearly from FIG. 3 mounted at the side of the chain and load trolley tracks 12, I6 and comprises a stop member 20 which is supported for longitudinal sliding movement back and forth from and into an operative position wherein it projects across the top of the track 12 and into the path of the depressible drive abutrnents on the load trolleys. Under normal conditions, the member 20 will be maintained in its operative or projected position into which it is urged by means of a spring 21. Mounted at the rear end of the slide is a pivoted dog 22 which is normally maintained in the position shown in FIG. 3 by means of a counterweight 23.

Mounted for pivotal movement about a fixed pivot post 24 is a bell crank lever 25 which is normally held in an inoperative position as shown in FIG. 4 by means of a spring 26. One of the arms of the bell crank lever 25 carries at its underside a cam follower roller 27 which is mounted for free rotational movement on a pin 28. Pivotally connected to the other arm of the bell crank level 25 is a link 29 by means of which said lever is coupled to a solenoid 30.

31 generally denotes a back stop assembly which in the embodiment illustrated comprises a roller 32 mounted on a stop arm 33 such stop arm being pivotally mounted and normally urged into its operative position by means of a spring. The ar rangement is such that normally the back stop which will be located below the track 12 will project into the path of the load-carrying trolleys or elements carried thereby. When the trolley is being driven from the drive chain it (the trolley) will normally brush past the back stop which will merely pivot idly and be returned to its operative position by the spring when the trolley has passed. In the event however that a trolley is stopped by the stop mechanism the back stop will then be effective to prevent undesirable rearward travel of the trolley i.e., movement of the trolley in the reverse direction to that in which it is normally driven. The back stop assembly may well take other forms but whatever its construction its function will be that indicated above.

To complete the stop mechanism a plunger 34 is provided such plunger which is loaded by a compression spring 35 being pivotally connected to an arm 36 which is in turn fixedly mounted on a shaft 37. The shaft 37 which is appropriately journaled for rotation about its longitudinal axis, carries at its lower end an arm 38 adapted to project into the path of a ramp or other appropriate element carried by the trolleys. Normally the plunger 34 is maintained in the position shown in FIGS. 2 and 4 but it is adapted on retraction of the stop member 20 to move under the action of its spring into engagement with a notch or recess in the side of said stop member thereby to lock the same in its retracted position. The notch or recess in the side of the stop member 211 is so dimensioned that when the plunger 34 is engaged therein said stop member will nevertheless be capable of a small overrunning or additional retractive movement.

The stop mechanismdescribed above is adapted to operate in the following manner:

Initially the parts will assume the position shown in the FIGS. 2-4 of the drawings with the stop member 20 projecting across the top of the trolley track 12. When a load trolley, which is being driven by a drive dog on the chain, reaches the stop mechanism, the stop member 20 will depress the drive abutment on the trolley thus causing the trolley to be disengaged from the influence of the chain dog. Any undesired reverse movement of the trolley which might be caused by load swing or inclination of the track 12 will be prevented by the back stop 31. Thus the trolley will be trapped between the stop member and the back stop and will be free from the influence of the drive chain.

To release the trolley, the solenoid 30 will be momentarily energized thereby to cause pivotal movement of the bell crank lever in a clockwise direction as shown which will bring the cam follower 27 into a position in front of the dog 22 on the stop member 20. The pivotal movement of the lever 25 will result in the second arm of such lever being caused to project across the top of the track 12 and into the path of the drive dogs on the drive chain. When a dog on the drive chain contacts the then projecting arm of the lever 25 it will by virtue of the movement of the chain impart a reverse i.e., a counterclockwise movement to the lever 25 so that the cam follower 27 which is then in contact with the dog 22 will push the latter thus causing the stop member 20 to retract. On retraction of the stop member 20 the spring loaded plunger 34 will move into engagement with the notch or recess on the side of said stop member and will effectively lock the same in its retracted position. Due to the slight overrun allowed to the stop member 20 by virtue of the dimensioning of the notch or recess, the cam follower 27 will, with continued counterclockwise movement of the lever 25, be disengaged from the dog 22 and the lever will be returned to its initial position under the action of its spring 26. It must be pointed out here that the solenoid 30 is energized only for a short duration sufficient to cause the lever 25 to assume its operative position.

With the stop member 20 retracted, the drive abutment on the trolley hitherto held will assume its operative position wherein it will be contacted by that drive dog on the chain which was effective to release the stop mechanism. As the trolley moves away from the stop a ramp or other element thereon will contact the arm 38 thereby causing a rotational movement of the shaft 37 and retraction of the plunger 34. With the plunger 34 retracted from the notch or recess in the stop member 20 the latter will be restored by means of its spring 21 to its initial position and the stop mechanism will then be ready for a further operating sequence.

The main advantages of a mechanism such as is described above may be summarized as follows:

I. Conveyor power is employed to retract the stop only a light solenoid being required to initiate the operation i.e., to move the lever 25 to its operative position.

2. The mechanism is fail-safe i.e., it does not require electrical or other form of power to return the stop member 20 to its normal position.

3. The load trolley is at all times under control as the drive dog on the chain which effectively releases the stop is the same dog which will subsequently be effective to drive the trolley.

I claim:

1. In a conveyor of the kind wherein load-carrying trolleys I are propelled along a fixed track by virtue of the engagement with drive abutments on said trolleys of drive dogs which depend from an endless driven chain travelling along a path above said fixed track, the provision at a selected station along the conveyor path of a stop mechanism comprising a stop member, biassing means biassing said stop member to assume normally an operative position wherein it will be effective to depress the drive abutment on any load carrying trolley arriving at the station thereby to effect discontinuance of the drive to said trolley, a member which, when it is required to release the trolley from the station, is movable into the path of the drive dogs on the driven chain, the latter member being operative, when contacted by one of said dogs to cause retraction of the stop member from its operative position thereby to allow the drive abutment on the trolley to return to its operative position so that said trolley will then be driven from the station, latch means operative to lock the stop member in its retracted position, and means adapted to be actuated b the load trolley as it moves away from the station to effect re ease of the latch means so that said stop member will return under the action of its biassing means to its operative position.

2. A stop mechanism as in claim 1 in which the stop member is supported for longitudinal sliding movement back and forth from and into its operative position wherein it extends transversely across the fixed track and into the path of the drive abutment on any approaching load trolley, said biassing means comprising a spring.

3. A stop mechanism as in claim 1 a pivoted abutment on the stop member, said abutment being biassed so as normally to assume an operative position, the member for causing retraction of said stop member comprising a bell crank lever which is mounted for angular movement about a fixed pivot and is urged into an inoperative position by means of a spring, the arrangement being such that on an initial angular movement of the lever from its inoperative position one arm thereof will be moved into the path of the dogs on the endless driven chain and contact of a dog with such arm will result in a reverse angular movement of the lever such as will cause the second arm thereof to cooperate with the abutment on the stop memberthereby to move said stop member into its retracted position.

4. A stop mechanism as in claim 3 comprising a solenoid to effect initial angular movement of the bell crank lever as a result of energization of the solenoid.

5. A stop mechanism as in claim 1 in which the latch means comprise a spring-loaded plunger operative on retraction of the stop member to engage a recess in the latter, said plunger being coupledto an arm which is carried by a rotatable shaft also carrying a further arm arranged to project with the path of any load trolley driven from the station, the arrangement being such that contact of a trolley with the further arm will result in angular movement of the shaft and resultant retraction of the plunger from engagement with the recess in the stop member. 

1. In a conveyor of the kind wherein load-carrying trolleys are propelled along a fixed track by virtue of the engagement with drive abutments on said trolleys of drive dogs which depend from an endless driven chain travelling along a path above said fixed track, the provision at a selected station along the conveyor path of a stop mechanism comprising a stop member, biassing means biassing said stop member to assume normally an operative position wherein it will be effective to depress the drive abutment on any load carrying trolley arriving at the station thereby to effect discontinuance of the drive to said trolley, a member which, when it is required to release the trolley from the station, is movable into the path of the drive dogs on the driven chain, the latter member being operative, when contacted by one of said dogs to cause retraction of the stop member from its operative position thereby to allow the drive abutment on the trolley to return to its operative position so that said trolley will then be driven from the station, latch means operative to lock the stop member in its retracted position, and means adapted to be actuated by the load trolley as it moves away from the station to effect release of the latch means so that said stop member will return under the action of its biassing means to its operative position.
 2. A stop mechanism as in claim 1 in which the stop member is supported for longitudinal sliding movement back and forth from and into its operative position wherein it extends transversely across the fixed track and into the path of the drive abutment on any approaching load trolley, said biassing means comprising a spring.
 3. A stop mechanism as in claim 1 a pivoted abutment on the stop member, said abutment being biassed so as normally to assume an operative position, the member for causing retraction of said stop member comprising a bell crank lever which is mounted for angular movement about a fixed pivot and is urged into an inoperative position by means of a spring, the arrangement being such that on an initial angular movement of the lever from its inoperative position one arm thereof will be moved into the path of the dogs on the endless driven chain and contact of a dog with such arm will result in a reverse angular movement of the lever such as will cause the second arm thereof to cooperate with the abutment on the stop member thereby to move said stop member into its retracted position.
 4. A stop mechanism as in claim 3 comprising a solenoid to effect initial angular movement of the bell crank lever as a result of energization of the solenoid.
 5. A stop mechanism as in claim 1 in which the latch means comprise a spring-loaded plunger operative on retraction of the stop member to engage a recess in the latter, said plunger being coupled to an arm which is carried by a rotatable shaft also carrying a further arm arranged to project with the path of any load trolley driven from the station, the arrangement being such that contact of a trolley with the further arm will result in angular movement of the shaft and resultant retraction of the plunger from engagement with the recess in the stop member. 